This application is based on Patent Application No. 10-276016 filed Sep. 29, 1998 in Japan, the content of which is incorporated hereinto by reference.
The present invention relates to an ink jet printing apparatus and more specifically to an ink jet printing apparatus having an improved recovery device for recovering or keeping in good condition an ink ejection performance of an ink jet print head.
Printing apparatus for printing a print sheet (also referred to simply as xe2x80x9crecording paperxe2x80x9d), such as paper, cloth, plastic sheet and OHP sheet, are being proposed in a construction capable of mounting print heads of various systems, including, for example, a wire dot system, a thermosensitive system, a heat transfer system and an ink jet system.
Of these printing apparatus, an ink jet printing apparatus (also referred to as an ink jet printer) that ejects ink from ink orifices to print on recording paper is a low-noise, non-impact type printing system and can perform a high-density, high-speed printing operation.
Generally, an ink jet printing apparatus has a means for driving a print head carrier, a means for feeding recording paper, and a means for controlling these means.
There are several types of energy generating elements for generating energy used to eject ink from orifices of the print head. They include an element that uses an electromechanical transducer such as piezoelectric material, an element which radiates electromagnetic waves such as laser to heat ink to eject an ink droplet by the action of heat, and an element that uses an electrothermal transducer having a heating resistor to heat the liquid.
A print head of an ink jet print system that ejects ink droplets by thermal energy is capable of printing at high resolution because the ink orifices can be arranged at high density. In the ink jet print system, a print head using the electrothermal transducer as an energy generating element is advantageous because it can easily be reduced in size and manufactured by fully utilizing the advantages of IC technology and microfabrication technique in the semiconductor field whose technical progress and reliability improvement are remarkable in recent years and because it can easily be increased in integration density and its production cost is low.
As described above, though it is an excellent print system simple in construction, the ink jet print system has problems that need to be solved.
One of the problems is stains formed around ink orifices on that surface (hereinafter referred to as a head face) of the print head which faces the print medium and in which ink orifices are formed. There are mainly two causes for the stains. A first cause for the stains is that when ink ejected for printing strikes the print paper, a part of the ink fails to adhere to the paper and bounces off. Further, when ink is ejected, miniscule ink particles, other than the main ink droplets contributing to the printing, may be formed and float in the air. These ink particles adhere to the head face, forming stains.
A second cause for the stains is ink droplets remaining on the head face during an ejection performance recovery operation, in which a cap is put on the head face to draw ink by suction from within the ink orifices in order to prevent clogging of the ink orifices and then is removed from the head face. When ink is drawn by suction, the cap is filled with ink. When in this condition the cap is removed from the head face, the ink in contact with the head face remains there. To prevent this, the head face may be treated with a liquid repulsive coating but this cannot expel residual ink completely.
Further, to remove ink remaining in the cap when the cap is taken off the head face after the ejection performance recovery operation is performed on the ink orifices, an thin plate-like absorbing body made of porous resin or nonwoven cloth is installed in the cap. If the absorbing body is not provided in the cap, when, with the cap open, the suction is performed to remove ink from the cap, only the ink in the immediate vicinity of the discharge port in the cap is drawn out, leaving the link at the surrounding areas. That is, the use of the absorbing body allows a negative pressure to act slowly so that the ink in the cap is drawn out by suction uniformly.
When unwanted ink droplets adhere to around the ink orifices, troubles occur, such as a so-called xe2x80x9ckinkxe2x80x9d in which the ink ejection direction deviates from the intended direction and an xe2x80x9cejection failuresxe2x80x9d in which ink cannot be ejected at all, degrading the print quality.
To solve this problem, a method is often adopted which wipes the head face with a blade (or wiper) as a wiping member made of an elastic material such as rubber (this operation is also referred to as xe2x80x9cwipingxe2x80x9d). The wiping method includes one which scans the print head with respect to a stationary blade to wipe the head face by the blade and one which holds the print head immovable and advances or pivots the blade to bring it into contact with the head face.
To prevent the blade and the print head from contacting each other unnecessarily hard, the former method may support the blade so as to be projectable toward the print head and set the blade in a projected position during the scanning of the print head in one direction only and in a retracted position during the scanning in the opposite direction. The latter method may reciprocally advance or reciprocally pivot the blade extending in a direction perpendicular to the main scan direction and properly advance or retract the print head to and from the blade scanning position. When the wiping is to be performed only during the forward movement for example, the print head is set at the corresponding position and, during the return movement, is retracted from that position.
However, when residual ink remains on the head face in large quantity, a large amount of ink will adhere to the head face wiping blade. As a result, when a means for cleaning the blade (cleaner) is provided, a large quantity of ink will adhere to the cleaner. This raises another problem of disposing of the ink wiped by the blade and of processing an ink receiving member such as cleaner.
Among the technologies that solve these problems and reduce the amount of ink remaining on the head face following the ink ejection performance recovery operation is Japanese patent Application Laying-open No. 11-138855 laid-opened on May 25, 1999.
Although the invention of the Japanese patent Application Laying-open No. 11-138855 (1999) can reduce the amount of ink remaining on the head face after the ejection performance recovery operation, a small amount of grain-like ink is found remaining in a case where there is a relative positional relationship between the cap and the in-cap absorbing body. In such a case it is known that ink often remains when the head engagement portion of the cap and the end portions of that surface of the ink absorbing body in the cap which is parallel to and nearest to the head face are close to each other.
To solve these problems experienced with the conventional systems it is an object of the present invention to provide an ink jet printing apparatus with an ejection performance recovery device which secures a predetermined space between the surface of the in-cap absorbing body facing the head face and the head engagement surface of the cap.
In the first aspect of the present invention, there is provided an ink jet printing apparatus comprising,
a cap for capping ink orifices provided on a head face of an ink jet print head,
an in-cap absorbing body disposed in the cap, and
a suction means for sucking ink from the ink orifices through the cap,
wherein the cap has a space formed along almost an entire circumference of a head engagement portion of the cap between an end surface of the in-cap absorbing body which is nearest to the head face and the head engagement portion of the cap.
Here, position restriction portions for the in-cap absorbing body may be provided in the cap and extend toward the end surface of the in-cap absorbing body.
Position restriction portions for the in-cap absorbing body may be formed integral with the in-cap absorbing body at location near the end surface of the in-cap absorbing body.
The height of the position restriction portions for the in-cap absorbing body may be lower than that of the end surface of the in-cap absorbing body.
A surface which is one step lower in height than the end surface of the in-cap absorbing body may be formed along an entire circumference of the in-cap absorbing body outside the end surface of the in-cap absorbing body.
A height of a portion of the in-cap absorbing body facing the ink orifices of the ink jet print head may be lower than that of the end surface of the in-cap absorbing body.
A portion of the in-cap absorbing body facing an array of the ink orifices of the ink jet print head and a portion of the in-cap absorbing body restricted by the position restriction portions may be lower in height than the end surface of the in-cap absorbing body and the position restriction portions may be provided on the in-cap absorbing body or on the cap at longitudinal ends of the in-cap absorbing body.
The in-cap absorbing body may be formed of a porous material.
The ink jet print head may have an electrothermal transducer for generating thermal energy to eject ink.
The ink jet print head may use thermal energy to generate a bubble based on a film-boiling in ink to eject an ink droplet.
In the second aspect of the present invention, there is provided a cap of an ink jet print head for capping a head face of the ink jet print head provided with an in-cap absorbing body installed in an interior thereof, wherein the cap has a space formed along almost an entire circumference of a head engagement portion of the cap between an end surface of the in-cap absorbing body which is nearest to the head face and the head engagement portion of the cap.
According to the ink jet printing apparatus of the present invention with the construction described above, a predetermined space is provided between the ends of that surface of the in-cap absorbing body which is parallel to and nearest to the head face and the head engagement portion of the cap. This construction can prevent ink from accumulating in small gaps between the ends of the in-cap absorbing body and the head engagement portion of the cap by the action of capillary attraction when the cap is open after the suction operation. This in turn prevents ink droplets from remaining on the head face and from being inadvertently transferred onto the print paper, and also reduces the total amount of ink that is wiped off by the next wiping operation. As a result, it is possible to prevent ink from being scattered from the wiping blade and blade cleaner into the interior of the apparatus, to reduce the amount of ink forced into the ink orifices during the wiping operation, and to reduce the amount of preliminary ejection ink required to discharge the forced-in residual ink from the orifices.
This space can be secured by forming in the cap the position restriction portions for the in-cap absorbing body that extend toward the ends of that surface of the in-cap absorbing body which is parallel to and nearest to the head face. The provision of this space ensures the above-described advantages.
Further, because the position restriction portions for the in-cap absorbing body are formed integral with the in-cap absorbing body at locations near the ends of that surface of the in-cap absorbing body which is parallel to and nearest to the head face, the position restriction portions can have an ink absorbing capability, thereby preventing more effectively the ink droplets from remaining on the head face and from being transferred onto the print paper.
Further, because the height of the position restriction portions of the in-cap absorbing body is set lower than that of the surface of the in-cap absorbing body parallel to and nearest to the head face, a space can be secured in the vertical direction (i.e., in the direction of thickness of the absorbing body) near the cap head engagement portions, thus further enhancing the above-mentioned advantages.
In addition, because a surface which is one step lower in height than the surface of the in-cap absorbing body parallel to and nearest to the head face is formed along an entire circumference of the in-cap absorbing body outside the surface of the in-cap absorbing body parallel to and nearest to the head face, it is possible to secure the space near and along the entire circumference of the head engagement portion of the cap, thereby reducing the amount of residual ink droplets which might be transferred onto the print paper.
Further, because at least a portion of the in-cap absorbing body facing an array of the ink orifices of the ink jet print head is set one step lower in height than the surface of the in-cap absorbing body parallel to and nearest to the head face, it is possible to prevent the in-cap absorbing body from directly contacting the nozzle portion of the head and degrading the ejection performance of the head. At the same time, because the in-cap absorbing body is formed to have a raised surface at a location near the ink orifices from which ink is ejected, the capability to collect residual ink is maintained and improved.
Further, the portion of the in-cap absorbing body facing an array of the ink orifices of the ink jet print head and a portion of the in-cap absorbing body restricted by the position restriction portions are set lower in height than the surface of the in-cap absorbing body nearest to the head face, and the position restriction portions are provided on the in-cap absorbing body or on the cap at longitudinal ends of the in-cap absorbing body. In this construction, the cross section of the in-cap absorbing body taken along a direction perpendicular to the array of ink orifices is basically the same at any position, except for a part of the longitudinal ends of the in-cap absorbing body when the position restriction portions for the in-cap absorbing body are provided. Hence, the in-cap absorbing body can be made by using a simple die structure whether it is formed by an extrusion method or a sintering method which heats powder filled in a die. The simple die structure facilitates the filling of material, improving the productivity of the in-cap absorbing body. In addition, this construction offers the advantages of being able to minimize the amount of residual ink droplets on the head face which may be transferred onto the print paper.
Further, because the in-cap absorbing body is made of a porous material, the ink can be properly absorbed.
Because the ink jet printing apparatus using an ink jet print head for printing comprises a cap and an ejection performance recovery means for recovering an ink ejection performance of the ink jet print head by drawing ink out of ink orifices of the print head with the print head capped by the cap, the ejection performance recovery operation can be performed through the cap satisfactorily.
Because the ejection performance recovery means has a means for applying a suction force through the cap to draw ink from the ink orifices, the ink can be properly discharged without contaminating the surroundings.
Further, because the ink jet print head has an electrothermal transducer that transforms applied electricity into thermal energy used to eject ink droplets, the ink ejection can be done properly to produce a clear printed image.
Furthermore, because the ink jet print head utilizes the film boiling in the ink caused by the thermal energy produced by the electrothermal transducer in order to eject ink droplets from the ink orifices onto the print medium, the printing can be performed well producing a clear printed image.
The above and other objects, effects, features and advantages of the present invention will become more apparent from the following description of embodiments thereof taken in conjunction with the accompanying drawings.